Composite protective sheet material

ABSTRACT

A composite protective sheet material for covering a smooth surface of a transparent material, especially but not exclusively for covering the surface of a lens. It comprises a film substrate at least one main surface of which is covered by an adhesive coating. At least a part of the said at least one main surface of the substrate is free or substantially free of adhesive, or has less adhesive applied to it than does the rest of that surface, thereby to provide a finger lift region of the film at an edge of the surface covered thereby.

The present invention relates to a composite protective sheet materialfor covering a smooth surface of a transparent material, especially butnot exclusively for covering the surface of a lens, comprising a filmsubstrate and an adhesive coating which covers at least one main surfaceof the film substrate.

Such a sheet material is applied to such a smooth surface to cover itand thereby protect it from scratches or other damage prior to use.

A disadvantage of such a sheet material is that is that it is difficultto peel off when the time comes for the transparent material, whetherthe latter is in the form of a lens, a window, or the transparent coverof a computer screen, to be put into use, especially if the transparentmaterial is in the form of a lens for use in spectacles which arecurrently made thin so that their edges are especially thin.

The present invention seeks to provide a remedy.

Accordingly, the present invention is directed to a composite protectivesheet material as set out in the opening paragraph of the presentspecification, characterised in that at least a part of the said atleast one main surface of the substrate is free or substantially free ofadhesive, or has less adhesive applied to it than does the rest of thatsurface, thereby to provide a finger lift region of the film at an edgeof the surface covered thereby.

The sheet material may be elongate, for example in the form of tape,which may be a roll of tape, which may be wound onto a reel.

The said part may be an elongate strip. If the sheet material is alsoelongate, the strip may run along the length thereof. If the sheetmaterial is in the form of a tape, the said part may extend all the wayalong the tape. This provides the advantage that wherever the tape iscut transversely, a finger lift region will be provided. It alsoprovides the advantage of ease of manufacture, for example by securing ashort strip of paper or other material around a roller which is used toeven the spread of adhesive over the film substrate when the compositesheet material is manufactured.

The adhesive may be visually distinct from the film substrate, forexample it may be made visually distinct by being coloured with a die,to render the position of the finger lift region more evident. This isall the more so if the film substrate is transparent or at leasttranslucent.

The present invention extends to a lens having a surface covered by acomposite protective sheet material in accordance with the presentinvention.

An example of a composite protective sheet material made in accordancewith the present invention will now be described in greater detail withreference to the accompanying drawing, in which:

FIG. 1 shows a roll of tape made in accordance with the prior art;

FIG. 2 shows a view from above of a circular lens covered with a portionof the tape cut in the shape of a disc from the roll shown in FIG. 1;

FIG. 3 shows diagrammatically a roll of tape embodying the presentinvention;

FIG. 4 shows a view from above of a circular lens covered with a portionof the tape cut in the shape of a disc from the roll shown in FIG. 3;and

FIG. 5 shows diagrammatically and not to scale a cross-sectional view ofthe lens and cover shown in FIG. 4 taken in the plane indicated by theline V-V in FIG. 4.

The prior art tape 10 shown in FIGS. 1 and 2 comprises a compositeprotective sheet material for covering the surface of a lens, comprisinga film substrate and an adhesive coating which covers at least one mainsurface of the film substrate. The adhesive has been applied uniformlyover the entire main surface on one side of the tape, and thereforeattaches everywhere to that side of the circular lens to which it issecured as shown in FIG. 2.

The tape 12 embodying the present invention and shown in FIGS. 3 to 5comprises a film substrate 14 of substantially uniform thickness oftransparent terpolymer polyethylene and an adhesive coating 16 ofsubstantially uniform thickness of an acrylic based copolymer insolution, coloured with a green dye, which covers one main surface ofthe film substrate 14.

The substrate is substantially 100 mm wide and substantially 100 micronsin thickness. The roll of tape in FIG. 3 is about 35 m in length. Thecoating 16 is substantially 22 microns in thickness.

FIG. 3 shows a roll of the tape 12 wound on a reel 18. In FIGS. 4 and 5,a circular portion of tape 12 from the roll shown in FIG. 3 has been cutto substantially exactly the dimensions of a plastics lens 20 onesurface 22 of which the tape 12 covers, to protect that surface 22against scratching and other possible damage.

However, unlike the prior art tape 10, the tape 12 shown in FIGS. 3 to 5is formed with an area in the form of a strip 24 running the entirelength of the roll shown in FIG. 3 and therefore across the entire widthof the circle of tape, as shown in FIG. 4, in which strip there is noadhesive on the film substrate 14. The strip lies substantially midwaybetween the edges 25 a and 25 b of the tape 12.

As a result, although the lens surface under the strip 24 is covered andtherefore protected by the film substrate 14, there is a small voidbetween the lens 20 and the film substrate 14 under this strip 24, whichprovides finger lift regions 26 and 28 where the strip 20 meets the edgeof the lens 20. The position of these regions 26 and 28 is made evidentto the user by virtue of the transparency of the film substrate 14 andthe fact that the adhesive of the coating 16 is coloured green, so thatthe strip stands out as more or less colourless against the green of theadhesive. In these regions 26 and 28, because of the absence of adhesive16, it is easier for the user to insert a fingernail for example to liftthe tape 12 and then to peel it off the lens 20 when the lens 20 is tobe prepared ready for use.

The strip 24 is substantially 9 mm wide.

Instead of terpolymer polyethylene, the film substrate 14 may be one ofpoly(ethylene/acid) copolymer, or polyethylene ethyl vinyl acetate, forexample, or indeed of any suitable plastics material that will readilyoccur to those of the art. Instead of an acrylic based copolymer insolution, the adhesive of the coating 16 may be one of a modifiedacrylic copolymer or a hydrocarbon resin, or indeed any adhesive thatwill readily occur to the reader of the art as being suitable. Theadhesive may be solvent based, water based or hot melt. It may becoloured or otherwise shaded any colour or shade other than green, andit does not have to be coloured or shaded at all although this willassist in showing the finger lift regions.

The width of the tape 12 may vary from 50 mm or less to 200 mm or more.It may have any length beyond about 50 mm. The thickness of the filmsubstrate 14 may be from 100 microns to 130 microns, or it may be from50 microns, or less, to 200 microns, or more. The thickness of theadhesive coating 16 may be substantially 15 microns, or from 5 microns,or less, to 50 microns, or more.

The width of the strip 24 may be from 7 mm to 10 mm, although it may benarrower or wider, provided it is not so wide that it creates anunacceptable risk of accidental peeling from a lens for example, nor sonarrow that it does not afford assistance in enabling the sheet materialto be peeled off a lens for example. The strip 24 may be off centre asregards its position across the width of the tape 12, provided it isspaced from the edges thereof. The area in which adhesive is absent orat least thinner does not have to be a strip 24, but may comprise aplurality of circles or other shapes for example spread over the filmsubstrate 14.

The tape 12 may be provided with a releasable peel-off backing (notshown) which covers the adhesive coating 16.

The plastics of the lens 20 may be allyl diglycol carbonate or any othersuitable plastics material such as polycarbonate. The material of thelens may instead comprise glass.

Many other modifications and variations to the tape 12 shown in FIGS. 3to 5 may occur to the reader without taking the resulting constructionof tape outside the scope of the present invention.

1. A composite protective sheet material for covering a smooth surfaceof a transparent material, especially but not exclusively for coveringthe surface of a lens, comprising a film substrate and an adhesivecoating which covers at least one main surface of the film substrate,wherein at least a part of the said at least one main surface of thesubstrate is free or substantially free of adhesive, or has lessadhesive applied to it than does the rest of that surface, thereby toprovide a finger lift region of the film at an edge of the surfacecovered thereby.
 2. A sheet material according to claim 1, wherein thesheet material is elongate.
 3. A sheet material according to claim 2,wherein the sheet material is in the form of tape.
 4. A sheet materialaccording to claim 3, wherein the sheet material is in the form of aroll of tape.
 5. A sheet material according to claim 4, wherein thesheet material is wound onto a reel.
 6. A sheet material according toclaim 1, wherein the said part is an elongate strip.
 7. A sheet materialaccording to claim 2, wherein the strip runs along the length of thesheet material.
 8. A sheet material according to claim 4, wherein thesaid part extends all the way along the tape.
 9. A sheet materialaccording to claim 1, wherein the adhesive is visually distinct from thefilm substrate, to render the position of the finger lift region moreevident.
 10. A sheet material according to claim 9, wherein the adhesiveis coloured with a dye.
 11. A sheet material according to claim 1,wherein the film substrate is translucent.
 12. A sheet materialaccording to claim 11, wherein the film substrate is transparent.
 13. Alens having a surface covered by a composite protective sheet materialas claimed in claim
 1. 14. A method of making a sheet material accordingto claim 1, wherein a strip of material is secured around a roller whichis used to even the spread of adhesive over the film substrate.